180dpi.....how do I get something larger?...600?

[mackb]

At the local print shop I was asking about getting a canvas print. The employee there told me my digital picture would have to be 600dpi. when I took a raw image and saved it as a Tiff it was 180dpi. I have always just looked at the resolution (ie 3200x2200). So my question is How big should I be able to print a picture if it is captured the best possible way with my 10d.

[Scottes]

600 DPI is a bit much. 300 is generally the standard, AFAIK, and I've seen as low as 240 look quite decent if you have it at arm's length. The Fuji Frontier, as an example, prints at 280 DPI.

Remember that that DPI only describes how the printer should print it. So your photo at 600 DPI would print at only 5.3 x 4.6. At 280 DPI the very same image would print at 11.4 x 7.8. The image doesn't change, just the print.

[SoCal69]

Assuming you must have 600 dpi, your maximum print size would be:

3072/600 x 2048/600 == 5.1 inches x 3.4 inches off the originally shot image. Of course, you can always upsize this through PS or other interpolation software.

[robertwgross]

If you have a digital file that is too small (like 100 DPI) for the print that you are trying to do, the other possibility is to do some interpolation. You could easily double or quadruple the file size.

Have you ever heard the phrase, "You can't make a silk purse out of a sow's ear"?

People get all kinds of mixed results when they interpolate upward. If you do in in a plain fashion, then you may or may not get any real gain in image quality. It may just move the apparent dots around a bit.

Some others have very intelligent interpolation programs, and these tend to get better results (maybe good enough for you). To get best results, it takes some trial and error to train the operator how to do it.

---Bob Gross---

[hammysd]

I assume you are using the 10D or the digital Rebel ie., you are at 6.3 MP and you are using the RAW format.

To repeat, your image has 6.3MP.

What size would you like. Take your image into Fred Miranda's action (download from his site for a small fee ) and the Photoshop action increases the size of your image. I just did this and my images at 15 inches by 23 inches are near photographic quality. These images are extremely sharp even at this size.

Fred's action uses a Photoshop "trick". By increasing your image by less than 10% each time you increase your image, the image doesn't seem to lose its sharpness. You can incease your image several times to get it to the size you want -- like 10 to 15 times -- but Fred Miranda's action is, of course, quite a bit quicker.

Before you put your image into this step process, you might want to use Unsharp Mask. Again, Fred Miranda has an action to complete this automatically with usually terrific results.

My results are spectacular. I then have my poster size image laminated to give it that post card shine -- the WOW! factor.

I'll go larger than 15" x 23" soon but I KNOW you will like your results even at the stated 180 dpi. Next time if you save in RAW try to get the program to save the RAW image at 300 dpi as it goes into Photoshp and you'll ensure terrific results.


hammysd

[drisley]

Programs that use Vector Interpolation, like Q-Image, also produce amazing results when up-sizing.

[Jim_T]

Assuming you must have 600 dpi, your maximum print size would be:

3072/600 x 2048/600 == 5.1 inches x 3.4 inches off the originally shot image. Of course, you can always upsize this through PS or other interpolation software.

SoCal69 is completely right..

The DPI is simply the number of pixels in an image divided by the number of inches you want to print it at. Print is the operative term here, since unless you actually print an image, the DPI setting is meaningless.

If number of pixels / dpi = inches .. then.. inches x dpi = number of pixels

So, to find out how many pixels you need for a particular print size at 600 dpi, use this fomula:

Horizontal print size in inches x 600
Vertical print size in inches x 600

Example:

If you want to print an 8 x 10" image at 600 DPI, you need

8 inches x 600 dpi = 4800 pixels
10 inches x 600 dpi = 6000 pixels

So to print an 8 x 10 image at 600 dpi, you MUST have an image that's 4800 x 6000.

As others have mentioned, if you don't have enough pixels in your image, then you have to 'make' extra pixels by interpolating.

[evilenglishman]

Before you put your image into this step process, you might want to use Unsharp Mask. Again, Fred Miranda has an action to complete this automatically with usually terrific results.
hammysd


You should NOT sharpen an image before up-scaling it!!
This will degrade your image.
The reason is that when you sharpen an image you are increasing edge contrast - in an extreme example you would see black lines and white lines along edges which some refer to as 'halo-ing'.
If you sharpen an image and then upscale it you are magnifying this effect. i.e a halo of 1 pixel becomes 10 pixels etc etc.

mackb - you dont say what the final print size will be????
as a guide:
a 15x10 print should be 4500x3000 (38.7mb) pixels regardless of dpi
a 12x8 print should be 3600x2400 pixels (24.8mb) regardless of dpi
a 10x8 print should be 3000x2400 pixels (20.6mb) regardless of dpi
a 9x6 print should be 2700x1800 (14mb) pixels regardless of dpi
a 6x4 print should be 1800x1200 (6.2mb) pixels regardless of dpi
file size (##mb) is the size of the image when opened

the dpi is only an issue on home printers and magazine printing etc.
When you send images to be printed on photographic paper the dpi is irrelevent as they are continuous tone images - i.e no dots or lines.

[billfranklin]

So far, the largest print I have made from my D60 is a 30x40 using Fred Miranda's Action. Result was amazing and I could not not tell the difference from a print that size made from medium format film. I use Pounds lab in Dallas TX, and I have to send them a file at 200 dpi in jpeg format. With a 10D, I would expect even better results.

Bill F.

[GenEOS]

I would question the 600dpi requirment also. 250-300 should do well for your application....